XK0-006 Practice Test 1 — 10 Questions

Question 1

A system administrator needs to configure a cron job to run a script every Monday at 3:00 AM. Which two cron expressions are correct? (Select TWO).

Accepted Answer

0 3 * * 1. The cron expression `0 3 * * 1` schedules the script to run at minute 0, hour 3 (3:00 AM), every day of the month (`*`), every month (`*`), and on Monday (day-of-week 1, where 0=Sunday, 1=Monday). Option E is correct because cron also accepts three-letter abbreviations for days of the week, so `Mon` is equivalent to `1`.

Answer

0 3 * * 0

Answer

0 3 1 * 1

Answer

0 3 * * 1-5

Question 2

A security analyst is investigating a potential breach and needs to examine user login history. Which THREE commands or log files provide information about user logins? (Select THREE.)

Accepted Answer

last. The `last` command reads the /var/log/wtmp file to display a list of all user logins and logouts since that file was created, showing timestamps and source IPs. This makes it a primary tool for investigating login history during a breach.

Answer

/var/log/syslog

Answer

/var/log/messages

Question 3

An administrator needs to replace all occurrences of 'oldhost' with 'newhost' in the configuration file /etc/hosts. Which command will perform the replacement and save the changes directly to the file?

Accepted Answer

sed -i 's/oldhost/newhost/g' /etc/hosts. The `-i` flag (in-place editing) tells `sed` to write the changes directly back to the file specified. Without `-i`, `sed` only prints the modified output to stdout and does not alter the original file. The substitution command `s/oldhost/newhost/g` performs a global replacement of all occurrences of 'oldhost' with 'newhost' on each line.

Answer

sed 's/oldhost/newhost/g' /etc/hosts

Answer

awk '{gsub(/oldhost/,"newhost")}1' /etc/hosts

Answer

grep -r 'oldhost' /etc/hosts | sed 's/oldhost/newhost/g'

Question 4

A Linux system fails to boot and displays a kernel panic immediately after the GRUB menu. The administrator needs to boot into a rescue environment. Which GRUB boot parameter should the administrator add to the kernel line?

Accepted Answer

systemd.unit=rescue.target. When a Linux system experiences a kernel panic immediately after GRUB, the administrator needs to boot into a minimal rescue environment that loads essential system services. The `systemd.unit=rescue.target` parameter tells systemd to start the rescue target, which mounts the root filesystem and starts only the most basic services, allowing the administrator to diagnose and repair the system. This is the proper GRUB kernel parameter for systemd-based distributions to enter a rescue shell without fully booting into the default multi-user or graphical target.

Answer

single

Answer

init=/bin/bash

Answer

quiet splash

Question 5

A user cannot start the Apache web service. The command 'systemctl start httpd' returns 'Failed to start httpd.service: Unit not found.' What is the most likely cause?

Accepted Answer

The httpd package is not installed. The error 'Failed to start httpd.service: Unit not found' indicates that systemd cannot locate a service unit file for httpd. This most commonly occurs when the httpd package (Apache HTTP Server) is not installed on the system. Without the package, no service unit file exists under /usr/lib/systemd/system/, so systemctl cannot start the service.

Answer

Network configuration is incorrect

Answer

Incorrect file permissions on /etc/httpd/

Answer

Disk space is full

Question 6

A security policy requires that SSH access be allowed only from the internal management subnet 10.10.10.0/24. Which firewalld rich rule should be added?

Accepted Answer

firewall-cmd --add-rich-rule='rule family="ipv4" source address="10.10.10.0/24" service name="ssh" accept'. It uses the firewalld rich-rule syntax to explicitly define an IPv4 rule that accepts SSH traffic only from the 10.10.10.0/24 source subnet. Rich rules provide granular control over source addresses, services, and actions, which is required by the security policy. The `--add-rich-rule` option allows specifying the rule family, source address, service name, and accept action in a single, persistent rule.

Answer

firewall-cmd --permanent --add-port=22/tcp --add-source=10.10.10.0/24

Answer

firewall-cmd --add-source=10.10.10.0/24 --add-service=ssh

Answer

iptables -A INPUT -s 10.10.10.0/24 -p tcp --dport 22 -j ACCEPT

Question 7

A Linux server experiences a kernel panic after a recent driver update. The system is still operational but unstable. Which command should be used to gather detailed information about the kernel modules currently loaded?

Accepted Answer

lsmod. B is correct because `lsmod` lists all currently loaded kernel modules by reading the `/proc/modules` file, showing their size, usage count, and dependencies. In a kernel panic scenario after a driver update, this command quickly reveals which modules are active, helping identify the problematic driver without further destabilizing the system.

Answer

modinfo

Answer

dmesg

Answer

modprobe -l

Question 8

A system administrator wants to limit the number of simultaneous logins for a user to 2. Which file and parameter should be configured?

Accepted Answer

/etc/security/limits.conf: username hard maxlogins 2. The `/etc/security/limits.conf` file allows setting resource limits per user or group, and the `maxlogins` parameter specifically controls the maximum number of simultaneous logins for a user. The syntax `username hard maxlogins 2` enforces a hard limit of 2 concurrent sessions for that user, which is the exact requirement. This limit is enforced by the PAM module `pam_limits.so`, which must be configured in the appropriate PAM stack file (e.g., `/etc/pam.d/login` or `/etc/pam.d/sshd`).

Answer

/etc/pam.d/login: session required pam_limits.so

Answer

/etc/security/limits.conf: @users hard maxlogins 2

Answer

/etc/security/limits.conf: username soft nproc 2

Question 9

A script uses 'set -e' and then calls a function that returns a non-zero exit status. The script exits unexpectedly. Which of the following should be added to the function to prevent the script from exiting?

Accepted Answer

set +e inside the function. The `set -e` directive causes the shell to exit immediately if any command returns a non-zero exit status. When a function called from such a script returns a non-zero status, the script exits. Adding `set +e` inside the function disables this behavior for the function's scope, allowing the function to handle errors internally without terminating the entire script.

Answer

return 0 after the command

Answer

exit 0

Answer

trap '' ERR

Question 10

A DevOps engineer wants to reduce the size of a Docker image by combining build stages. Which Dockerfile feature should be used?

Accepted Answer

Multi-stage builds (multiple FROM statements). Multi-stage builds, implemented by using multiple FROM statements in a single Dockerfile, allow a DevOps engineer to copy only the necessary artifacts from intermediate build stages into the final image. This eliminates build-time dependencies, tools, and intermediate layers from the final image, significantly reducing its size without sacrificing build functionality.

Answer

RUN --mount=type=cache

Answer

Layer caching

Answer

Using a smaller base image like Alpine